Connectivity dynamics and its impact on material flux and transformations in a watershed

Abstract

Connectivity of a landscape is recognized in hydrology, ecology, and geomorphology as an important driver of resource redistribution within and between catchments. Catchment hydrologic connectivity can be described as the emergent property of a system resulting from the interaction of its inherent landscape properties, weather events, and the changing climate, as well as the influence of these factors on the ability of the system to transport water and constituents through the system. The magnitude and frequency of events that hydrologically link landscape units are thought to relate closely to the ecological integrity of landscapes (Freeman et al. 2007, Pringle 2003). In this study, an improved understanding of connectivity is sought through the development of a new conceptual framework and its application for the modeling study of a small agricultural field. The framework recognizes the complex interactions between rainfall variability, landscape heterogeneity, antecedent soil moisture conditions, and thresholds, which contribute to the hydrologic behaviors and response of a catchment observed across spatial and temporal scales. The model provides a context in which these emergent behaviors can be studied. The Precision Agricultural Landscape Modeling System was adapted to simulate the study site, which has a flat topography, five different soil regions, agricultural tile drainage, and four different vegetation types that include bioenergy crops. It was found that tile drains, soil texture, and vegetation type are the dominant determinants of the hydrological responses of the field, giving rise to spatiotemporal patterns of soil moisture. This study is a first step in using a model and the connectivity framework in combination to pursue fine-scale understanding of a human-altered landscape, which could be used to better predict ecohydrological responses at a larger basin scale.